We're always being promised a future that never quite gets here. It's time for a change. Take a look at these ten automotive innovations, chosen by Jalopnik readers, that haven't gotten off the ground yet, but we're told they still could. Yeah, sure they will.

In the world of cars, both automakers and private inventors have come up with new technologies that …
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Welcome back to Answers of the Day — our daily Jalopnik feature where we take the best ten responses from the previous day's Question of the Day and shine it up to show off. It's by you and for you, the Jalopnik readers. Enjoy!

Why we want it built: We can leave the nitty-gritty details to engineers. They solve practical problems. Our job is to dream big, and what we really want in our cars aren't slightly more efficient transmission and tire combos. What we want are pint-sized nuclear reactors burning clean, quiet radioactive fuel.

How soon until I can buy one: Remember those practical problems that we gave to the engineers? Well, they came back and stapled a list of them to our foreheads. It seems that making a nuclear reactor that fits into your trunk is kinda hard, and their latest prototype vaporized the driver, and then its nuclear fuel was hijacked by North Korea. So there are a few kinks to work out.

Why we want it built: In contrast to nuclear power, solar power won't give you a third arm or turn you into a superhero. Solar-powered cars have been around for a while, and we love the idea of effortlessly clean solar energy powering the Camrys and Malibus of our future. Why settle for anything less?

How soon until I can buy one: Solar power is getting closer to mass affordability, but we are still a long way off. We also haven't figured out how you everyone will drive in winter. If you live in New Mexico or western Australia, you should be fine. The rest of us may have to wait a while.

Why we want it built: I myself am no expert at thermodynamics, but it's clear to me that a tequila-burning jet engine is the ideal power plant for any car. We look forward to a future when automotive designers forgo the superior efficiencies of diesel and go for the awesome that is turbine-hybrid propulsion.

How soon until I can buy one: If you have enough cash - I'm guessing something between Bugatti money and private racetrack money - you'll be able to buy the one-off turbine-hybrid supercar, the Jaguar C-X75 concept (the production version won't have any diesel micro-turbines). For everyone else, you'll have to spend your time building Chrysler replicas in your garage, because in the conservative, cost-centric car world, turbines are a long way off.

Why we want it built: The more you get to know about cars, the more you can see that so many of them share the same bones under their superficially different skins. Why leave the platform sharing to the manufacturers when you could just buy the basic chassis and swap out bodies as you please? If everything that makes a car go, stop, and turn is contained in a flat skateboard-type deal, you could change cars like you change your clothes. You could have a minivan to drop the kids off for school, a sports car to get to work, and a stylish sedan to do the errands and go out to dinner. It's a no-brainer, right?

How soon until I can buy one: If you spend your days accruing ungodly sums of money and GM boardroom contacts, you could own one today. GM built a skateboard-type fuel cell show car in the early 2000s, and we bet it's still humming around some California test facility. For all the components necessary to make the whole mix and match body styles thing to work is still a massive undertaking. You don't just need to bring the advanced technology to market, which would take years in its own right, but you'd have to kit out a whole dealership network with training, parts, and plenty of spare shells. Give it a few decades, eh?

Why we want it built: People may have lauded the Smart Car when it came to the market as a bold new design. Where other cars parallel parked, the Smart could pull up straight to the curb, like an old Isetta. But why bother parking at all? Why not have cars fold in two, so they stand upright and slot together like shopping carts? It's usually something you just associate with the Jetsons, but in the real world you could fit cars together in unbelievably tight garages and city streets wouldn't be crowded any more with endless rows of curbside beige sedans and SUVs.

How soon until I can buy one: Well, MIT has a working prototype, but it looks like it's going to be a few decades before car dealerships start looking like closets, with new cars scrunched together like clothes on a rack.

Why we want it built: If only there was a fuel that burned clean and never ran out...oh wait! There's hydrogen! For the past few decades hydrogen powered cars haven't been much more than a way for carmakers to show off some green cred concept cars without much hope for production, but there are a couple dozen, maybe even a hundred fuel cell cars pootling around the globe, leaving little but water and a faint whiff of the future in their wake. A special mention goes to BMW's hydrogen combustion engines, which are probably much less efficient than the ruthlessly electric fuel cell, but are significantly more awesome. Who doesn't want to drive around with a bunch of tiny Hindenburgs under the hood?

How soon until I can buy one: Today, if it wasn't for the shadow government illuminati plots to burn holes in the ozone to sell us more sunscreen!!! Actually, just head over to the California Fuel Cell Partnership between Davis, CA and Sacramento with a cool million in your briefcase and I'm sure you'll be able to work something out. I bet there are some spare fuel cells Toyotas lying around.

Why we want it built: We've certainly moved on from the days of farmers laying out nails in the road to pop the tires of unsuspecting turn of the century automotive enthusiasts, but there's still so much we have ahead of us. Why have inflatable tires at all, dealing with flats and everyday wear and tear? Tires are something we deal with, not something we enjoy- tweels take so much of the hassle out of the equation with a simpler, cooler solution.

How soon until I can buy one: Tweels are around, in all of their questionably-named glory. I doubt that your next car will have them, but in the super-simplified United States of Wonderful Happiness(™) of your kids' generation, you may start seeing them on the road, and not just on the Lunar Rover.

Why we want it built:If you don't really understand how cars work, every time you look under a car you see the spinning, death-tempting axles and gears that connect a car's engine to its wheels. Why it couldn't all just be so much simpler? In-wheel motors take a lot of the complexities of designing a car out of the equation. You can have a whole drivetrain tucked into the wheels, leaving the passenger cell to take any shape you please. Your wheels won't be so viciously tethered to a single engine, and could easily turn in on each other, making cars move more like people and less like two ton land barges.

How soon until I can buy one: Even more so than airless tires, carmakers have been teasing us with in-wheel motors for years now. Ever since electric cars came back into vogue, we've seen these things parading through the show car circuit, but it could still be another decade or two before anything production ready rears its super-agile head.

Why we want it built: A flying car is a horrible idea. Cars and planes just aren't built the same, and every time we've seen people try and build a flying car, we've either ended up with a jack-of-all-trades, or a straight up manslaughter machine. I don't care to rehash how many enterprising people have died trying to make planes out of Pintos and the like, but the two things just don't really go together. None of these reasons do anything to dampen our enthusasm for flying cars, though. Why keep us tethered to the roads, especially when they're so damn overcrowded as it is?

How soon until I can buy one: It depends on who you ask, but Terrafugia says they're on the cusp of creating "roadable aircraft." And then there's this guy.

How soon until I can buy one: Driverless cars are very much present in the world of 2011, though you can't really buy one yet. We're glad, too, because it still looks like there are some kinks to work out that should probably be addressed before I let my 92-year-old grandma behind the wheel of a self-driving car.